Question

circles end - of - lesson test
8 if the radius of a circle with an area of 12.56 mm squared is multiplied by 5, what is the area of the new circle?
314 mm squared
78.5 mm squared
62.8 mm squared
39.43 mm squared
skip 7/10 complete

Explanation:

Step1: Recall the area formula for a circle

The area formula of a circle is $A = \pi r^{2}$, where $A$ is the area and $r$ is the radius. Given the initial area $A_1=\pi r_1^{2}=12.56$ mm².

Step2: Find the new - radius

The new radius $r_2 = 5r_1$.

Step3: Calculate the new area

The new area $A_2=\pi r_2^{2}=\pi(5r_1)^{2}=25\pi r_1^{2}$. Since $\pi r_1^{2}=12.56$ mm², then $A_2 = 25\times12.56=314$ mm².

Answer:

314 mm squared